Retail shelving systems often include a base to which generally vertical, upright tubing is attached. The tubing typically includes slots or the like for receiving shelf brackets upon which shelves are supported. In the retail shelving industry, it is common for extensions to be inserted in the open top ends of upright tubes to gain additional space to hang shelves.
Prior art extensions typically employ connectors that are “X” shaped and fabricated from flat steel components. These are light duty designs, however, and thus are not capable of carrying heavy shelf loads and generally are not used to connect entire uprights to their base legs.
Other connectors for joining tubing have been developed. These include the connectors described in U.S. Pat. No. 5,904,437 to Allen; U.S. Pat. No. 6,062,761 to Allen; U.S. Pat. No. 5,464,299 to Scharer et al.; U.S. Pat. No. 6,874,971 to Albaugh and U.S. Pat. No. 4,161,375 to Murphy. While these designs may be effective, they employ threaded fasteners and/or are difficult to manufacture which increases cost and complexity of use.
Furthermore, most existing upright tubing designs are large, welded assemblies that are bulky and cumbersome to handle. This presents challenges both in manufacturing and shipping. The parts occupy a large amount of space on the paint line and require non-standard pallets for shipping. By splitting the upright tubing into two sub assemblies or sections, standard size pallets can be used and the parts will hang more densely on the paint line thus reducing manufacturing and shipping costs.
Most previous attempts to create a two-piece upright have employed connections designed to fit snugly within the upright tube. The problem with this approach is that the internal dimensions of the tubing can vary greatly due to normal manufacturing tolerances. As a result, it is extremely difficult to create a joint that is consistently tight to prevent deflection of the uprights when the shelves are assembled and loaded.